High pressure fluids solid lines

Figure 9.22 Schematic PT diagrams for the five major classes of binary fluid mixtures. Large dots are pure vapor-liquid critical points dashed lines are pure vapor-pressure curves. Solid lines starting from the pure, high-pressure critical point are mixture vapor-liquid critical lines other solid lines are mixture liquid-liquid critical lines. Small dots are upper (U) and lower (L) critical end points dash-dot lines are three-phase VLLE lines. Diagrams shown here are representative of the classes, but they do not exhaust the possibilities.

This method has a number of positive features it may be applied to most supercritical fluids with critical temperatures close to ambient deposition of the solid product occurs in a controlled manner, if necessary under an inert atmosphere and the high pressure "stabilizing" conditions are maintained right up to the point of precipitation. The precipitated solid product may then be analysed and characterised by other off-line spectroscopic techniques. In our example, the 13C-NMR spectrum of the solid material, redissolved in d8-toluene, shows the same resonances as those observed with a genuine sample of Cr(CO)4(C2H4)2. 

The high-pressure limits of gas-gas equilibria have been recently discussed by Streett. In principle there is no limit of the gas-gas critical curve to higher temperatures and pressures.f Since dTjdp happens to be larger for a three-phase line fluid-fluid-solid than for the gas-gas critical curve the most probable behaviour, however, will be that the region of gas-gas equilibria disappears below the crystallization surface at high temperature and pressure and that the gas-gas critical curve ends at a critical end point on the three-phase line GGS (preferably GGSii) which is more or less an extension of the three-phase line LLS.J An... 

In Fig. 11, we draw schematically the case of fluid-solid phase behavior for the Type-I fluid mixture water-NaCl. For critical temperatures this far apart, the three-phase line Sb-L-V from the low-temperature quadruple point (where four three-phase lines meet) to the solutes triple point develops a high maximum that reaches above water s critical pressure and temperature. If a salt solution is heated at a pressure above the critical pressure of water, the vapor-liquid critical line is crossed first, and a two-phase L-V region entered. At high enough temperature the three-phase line Sb-L-V may be crossed, and solid salt will form. Thus supercritical water, fully miscible with air constituents and hydrocarbons, becomes a poor solvent for salts. 

Dimensionless flow rate versus dimensionless pressure drop for helical annular flow of a power law fluid n = 1 is the Newtonian solution representing the result in the absence of shear thinning. The solid lines are the results obtained numerically, while the dashed line (for n = 0 is the analytical solution obtained using eq. 2.4.23. Note how much Q is enhanced at high pressures. 

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